Characteristic behavior of peroxyacetyl nitrate (PAN) in Seoul megacity, Korea

We measured the concentrations of peroxyacetyl nitrate (PAN) and other photochemically reactive species, including O(3), NO(2), and non-methane hydrocarbons (NMHCs), in the Seoul Metropolitan area (SMA) during May through June in 2004 and 2005. PAN was determined using a fast chromatograph with luminol-based chemiluminescence detection. Mixing ratios of PAN ranged from below the detection limit (0.1ppbv) to 10.4ppbv with an average of 0.8ppbv. O(3) concentrations ranged from 0 to 141ppbv. The average PAN/O(3) ratio of 0.07 was higher than that observed in cities of Europe and North America (0.02) where control strategies have been enforced to reduce hydrocarbon emissions through extensively reformulated gasoline programs. Strong positive correlations between daily PAN and O(3) maxima during the day demonstrate that similar photochemical factors controlled the production of these two chemicals. However, relationships between PAN and its precursors, NO(2) and NMHCs, suggest that PAN production was more sensitive to NO(2) than NMHCs levels whereas O(3) production was limited by the overall availability of NMHCs. It is likely that the compositions of NMHCs in SMA were favorable for PAN production because of the low fractions of oxygenated compounds in automobile fuels. PAN maxima were observed around noon, which was 2-3h earlier than the much broader O(3) maxima that occurred in the midafternoon. After reaching the maximum, PAN concentrations rapidly dropped within a few hours, which could be largely due to thermal destruction and to limited production under the typically low NO(2) levels that occurred in the early afternoon. The heterogeneous destruction of particulate matter could be an additional sink for PAN in SMA.     

Continuous measurement of peroxyacetyl nitrate (PAN) in suburban and remote areas of western China

Knowledge on atmospheric abundance of peroxyacetyl nitrate (PAN) is important in assessing the severity of photochemical pollution, and for understanding chemical transformation of reactive odd nitrogen and its impact on the budget of tropospheric ozone (O₃). In summer 2006, continuous measurements of PAN were made using an automatic GC–ECD analyzer with an on-line calibrator at a suburban site of Lanzhou (LZ) and a remote site of Mt. Waliguan (WLG) in western China, with concurrent measurements of O₃, total reactive nitrogen (NO_y) and carbon monoxide (CO). At LZ, several photochemical episodes were observed during the study, and the average mixing ratio of PAN (plus or minus standard deviation) was 0.76 (±0.89) ppbv with the maximum value of 9.13 ppbv, compared to an average value of 0.44 (±0.16) ppbv at remote WLG. The PAN mixing ratios in LZ exhibited strong diurnal variations with a maximum at noon, while enhanced concentrations of PAN were observed in the evening and a minimum in the afternoon at WLG. The daily O₃ and PAN concentration maxima showed a strong correlation (r² = 0.91) in LZ, with a regression slope (PAN/O₃) of 0.091 ppbv ppbv^?1. At WLG, six well-identified pollution plumes (lasting 2–8 h) were observed with elevated concentrations of PAN (and other trace gases), and analysis of backward particle release simulation shows that the high-PAN events at WLG were mostly associated with the transport of air masses that had passed over LZ.     

World-wide ambient measurements of peroxyacetyl nitrate (PAN) and implications for plant injury

Peroxyacetyl nitrate (PAN) is a major phytotoxic component of the photochemical oxidant complex in southern California, but its distribution and effects in other parts of the world are very poorly understood. Based on ambient air sampling at Riverside, California, in 1980, and published reports of PAN concentrations from other parts of the world, PAN concentrations in southern California appear to be five to ten times higher than those reported from eastern North America, western Europe, or Japan. PAN in Riverside, California, averaged 8.1 ppb in July, 9.4 ppb in September and 8.8 ppb in October 1980. These values represent the average of 48 measurements made at 15-min intervals between 0800 and 2000 LT. Potentially phytotoxic episodes, defined herein as PAN > 15 ppb for 4 h during the a.m. period or > 25 ppb for 4h in the p.m. period occurred 27 times in Riverside in 1980. These data were similar to PAN concentrations recorded in the mid 1960s in the Los Angeles Basin, indicating that PAN continues to be a serious air pollution problem in southern California. In contrast, PAN normally averages 1 ppb or less outside of southern California, and because of this low concentration, PAN by itself does not appear to be a major cause of photochemical oxidant injury to vegetation in those regions.     

Absorption of peroxy acetyl nitrate and ozone by natural surfaces

The dry deposition of PAN to grass, soil and water surfaces has been studied in a wind tunnel. Grass and soil were found to remove PAN with deposition velocity (vg) around 0.25 cm s⁻¹, but seawater and deionised water surfaces did not remove PAN at appreciable rates (v_g < 0.02 cm s⁻¹). The diurnal variation of PAN concentration at ground level can be explained in terms of photochemical production during daylight hours and deposition continuing during the night.     

Phytotoxicity of diuron alone and in combination with copper or folpet on duckweed (Lemna minor)

The photosystem II-herbicide diuron is widely used for weed control in Champagne's vineyards. Its important use and its relative persistence make it of particular interest for ecotoxicological studies. Toxicity of diuron was assessed on Lemna minor L., a representative aquatic macrophyte regularly used for toxicological studies. Toxicity assessments were based on inhibition of growth and total chlorophyll content of L. minor cultures after 7 days. Growth was inhibited and IC(50) and IC(90) were, respectively, 25 and 60 microg l(-1), but chlorophyll content of L. minor increased in response to the herbicide. When diuron was combined with copper, growth inhibition of L. minor depended on the concentrations of both chemicals. For some concentrations, combination of these chemicals resulted in a slight (but non-significant) antagonism. Additivity was observed for all other mixtures. When diuron was combined with folpet, growth and chlorophyll content of L. minor only depended on the concentration of the herbicide. Diuron was also found to prevent the copper-induced decrease of chlorophyll content when it was combined with this metal. A multifactorial model was found more appropriate to characterize interactions between pesticides than Abott's model.     

Assessment of ozone effects on nitrate export from Hubbard Brook Watershed 6

The impact of the air pollution ozone on soil N dynamics and temporal and spatial patterns of streamflow nitrate flux at the Hubbard Brook Experimental Forest Watershed 6 during the 1964-1994 period was assessed using aggregated (one-cell) and spatially explicit (208-cell) versions of the SImple NItrogen Cycle (SINIC) model. Simulated ozone effects included reductions in stomatal conductance and plant N demand. Model uncertainty was evaluated using Monte Carlo simulations. Ambient ozone was estimated to cause an additional 0.042 gN/m2 per year of nitrate export, 12% of the mean annual streamflow nitrate flux. The 95% credible interval of this estimate was 0.002-0.083 gN/m2 per year, or 0.72-27.3% of the annual flux. The large uncertainty in this estimate suggests that it may be difficult to identify ozone effects on nitrate export utilizing long term data from a single site.     

Photodegradation of the herbicide EPTC and the safener dichlormid, alone and in combination

Photodegradation of the herbicide EPTC (S-ethyl-N, N-dipropylthiocarbamate), and the safener dichlormid (2,2-dichloro-N, N-diallylacetamide) has been examined in methanol and in water solutions. Irradiation of EPTC and dichlormid with UV light at 254 nm caused rapid degradation in both media. Remarkable and gradual changes in color of EPTC irradiated solution was observed from clear to yellow then to intense orange. EPTC half-life of elimination in water was 14.0, and 18.5 min, and in methanol 37.2 and 32.2 min, when irradiated with and without dichlormid, respectively. There was significant difference between rate of EPTC degradation in water and methanol in the presence or in the absence of dichlormid. Negligible degradation of EPTC or dichlormid at > 290 nm was observed. Photoproducts were separated and identified using GC or/and thin-layer chromatography then identified using mass spectrometry. It appeared that some products have high molecular weight that formed as a result of dimerization. This is possibly a result of the coupling of radicals that formed through EPTC degradation. The cleavage of C-S and C-N bonds accounted for the formation of these radicals. Gradual dealkylation of the acid chains of EPTC has also occurred. EPTC-sulfoxide, EPTC-sulfone, Propylamine and dipropylamine were detected as photoproducts of EPTC at 254 nm. Dichlormid pathways of degradation at 254 nm were characterized as dechlorination, dealkylation, and hydrolysis both in water and methanol. The findings showed that dichlormid did not significantly affect EPTC photodegradation either at 254 nm or at > 290 nm. The biological/toxicological properties of the photoproducts need further study, particularly the dimer compounds.     

Blood concentrations of polycyclic musks in healthy young adults

Knowledge on the concentration of polycyclic musk fragrance compounds in human blood is sparse. This study examined the concentrations of six polycyclic musks in blood samples from healthy volunteers. Blood was taken from hundred healthy students of the Medical University of Vienna. The lipophilic fraction was extracted and after purification analyzed by GC-MS. Study participants also completed a questionnaire on the use of cosmetics, about nutrition and other life-style aspects. Two compounds -- galaxolide and tonalide -- were identified in higher percentages of the blood plasma samples. Maximum plasma levels over 100 ng/l were also only found for galaxolide (4100 ng/l) and tonalide (800 ng/l). Women showed significantly higher levels than men. In a statistical multivariate approach only use of body lotion and age were predictive of positive galaxolide concentrations. For tonalide no significant predictor could be found. The findings mirror the replacement of nitro musk fragrances by polycyclic musks, mainly galaxolide. The high concentrations of galaxolide in human blood raise concern since few toxicological data are available.     

Effects of thymol and carvacrol,alone or in combination,on fermentation and microbial diversity during in vitro culture of bovine rumen microbes

Two essential oils (EO), thymol and carvacrol, were used in six ratio (100:00, 80:20, 60:40, 40:60, 20:80 and 00:100) combinations of both EO and in a dose of 0.2?g L^?1 in bovine ruminal culture medium, 24-h cultures, to evaluate effects on total gas production (TGP), methane production, in vitro dry matter digestibility (IVDMD) and in vitro culture population dynamics of methanogenic and total bacteria. Total DNA extracted from ruminal microorganisms was subjected to denaturing gradient gel electrophoresis (DGGE)-polymerase chain reaction (PCR) to examine effects on bacterial populations. The effect of EO on TGP and IVDMD were assessed by comparison to untreated control cultures. In general, methane production by the microbial populations appeared to be higher with treatments containing the highest concentration of thymol than with treatments containing more carvacrol resulting in a tendency for greater methane-inhibiting activity achieved as the thymol concentration in the thymol:carvacrol mixtures decreased linearly. The population of total bacteria with a 74.5% Dice similarity coefficient for comparison of DGGE band patterns indicating shifts in bacterial constituents as EO ratios changed. No effects on TGP, IVDMD while only slight shifts in the methanogenic populations were seen with an overall 91.5% Dice similarity coefficient.     

Peroxyacetyl nitrate (PAN) in relation to ozone and some meteorological parameters at Delft in the Netherlands

Since 1972 concentrations of peroxyacetyl nitrate (PAN), one of the products of photochemical air pollution, have been measured every 15 min in ambient air at Delft. This paper describes the procedure as well as the results of 48 days of sampling in 1972.One conclusion is that, if one wishes to consider the complete diurnal variation of photochemical air pollution, the mean half-hour PAN concentrations provides a better criterion than mean half-hour ozone concentrations. In order to study long range transport of products of photochemical air pollution it is desirable to measure both ozone and PAN at more than one monitoring station.     

Effects of salinity and ozone,individually and in combination,on the growth and ion contents of two chickpea (Cicer arietinum L.) varieties

The aim of this study was to determine the effects of ozone and salinity, singly and in combination, on the growth and ion contents of two chickpea (Cicer arietinum L.) varieties. Chickpea plants were grown in non-saline and saline conditions, with and without a repeated exposure to ozone. Salinity at a concentration of 30 mM NaCl caused a substantial reduction in plant height, number of leaves and the dry weights of the leaves, stems and roots. Biomass allocation to the leaves increased, predominantly at the expense of the roots. Ozone at a concentration of 85 nmol mol(-1) for 6 h per day for 25 days reduced plant height and dry weights but had no effect on leaf number. The results show substantial effects of salinity and ozone on chickpea growth and ion concentrations. When ozonated plants are grown in the presence of salinity, further reductions in growth occur.     

Effects of ozone on managed pasture: I. Effects of open-top chambers on microclimate, ozone flux, and plant growth

Open-top chambers (OTC) were established in a field of managed pasture, and environmental parameters were recorded inside and outside to study the influence of OTCs on radiation, air temperature (T(air)), saturation vapour pressure deficit (svpd), and soil water content in relationship to plant growth and yield. Canopy development in OTCs supplied with non-filtered air (NF) and in ambient (AA) plots was followed by measuring leaf area index (LAI). The dry matter yield was determined after three growth periods in each of two consecutive seasons. Boundary layer conductance (g(bw)) and wind speed (u) were measured along a vertical profile, and day-time flux were measured along a vertical profile, and day-time flux of O(3) was estimated throughout the experiment on the basis of a mass balance. The vertical profile of u showed values in the range 1-1.2 m s(-1) at the top of the canopy, and maximum g(bw) was 20-25 mm s(-1). Average reduction in global radiation in OTCs was 25%, and volumetric soil water content was reduced by about 5%. Daily mean T(air) was increased by 1.3 degrees C, mean daily maximum svpd by 0.08 kPa, and the temperature sum (degree days with base temperature of +5 degrees C) by 12%. Fluctuations in the difference in daily mean T(air) and svpd during the daytime between OTCs and ambient air were related to canopy structure. Differences were largest after each cut and declined with increasing LAI. A small effect of changes in LAI on T(air) and svpd occurred during periods with low soil water content. The flux of O(3) in OTCs was largest (>100 microg m(-2) min(-1)) before and smallest (<20 microg m(-2) min(-1)) after each cut. Calculated deposition velocities for O(3) (nu(d)) in the range 0-3 cm s(-1) were generally higher than those measured under most field conditions. Overall, in OTCs the deficit in soil and atmospheric moisture was larger than in the open field, and the increase in daily mean T(air) was strongly influenced by the stage of canopy development. Changes in microclimate and incoming radiation affected pasture development. LAI was slightly reduced in OTCs as compared to AA plots. The total accumulated dry matter yield for all six growth periods was only about 7% lower in OTCs, but the contribution of clover to total forage mass declined during the experiment. OTCs had no significant effect on weeds. The results indicate that OTCs reduced the competitiveness of clover, and that the increase in growth of grasses compensates for the loss in clover yield. The shift in species composition caused by OTCs must be considered when studying the effect of pollutants on pasture.     

Adsorption, transformation, and bioavailability of the fungicides carbendazim and iprodione in soil, alone and in combination

When studying the effect of mixtures of toxic substances on soil organisms, attention must be paid to peculiarities in exposure to mixtures as opposed to that of single toxicants. The fungicides carbendazim and iprodione compete in the adsorption to soil. The presence of iprodione reduced the adsorption of carbendazim by 30%, while carbendazim reduced the adsorption of iprodione by 70%. Iprodione had little effect on the transformation rate of carbendazim in soil. However, carbendazim retarded the transformation of iprodione in soil by 26%. The concentration of the fungicides in pore water was found to be substantially higher for mixtures than when a fungicide alone was present in the soil. The effect of the additional fungicide on the concentration is especially apparent in the period following the first 1 to 2 weeks of the incubation. The inclusion of copper in the mixture has little additional effect on the concentration of the fungicides in pore water.     

Effects of simultaneous ozone exposure and nitrogen loads on carbohydrate concentrations, biomass, and growth of young spruce trees (Picea abies)

Spruce saplings were grown under different nitrogen fertilization regimes in eight chamberless fumigation systems, which were fumigated with either charcoal-filtered (F) or ambient air (O3). After the third growing season trees were harvested for biomass and non-structural carbohydrate analysis. Nitrogen had an overall positive effect on the investigated plant parameters, resulting in increased shoot elongation, biomass production, fine root soluble carbohydrate concentrations, and also slightly increased starch concentrations of stems and roots. Only needle starch concentrations and fine root sugar alcohol concentrations were decreased. Ozone fumigation resulted in needle discolorations and affected most parameters negatively, including decreased shoot elongation and decreased starch concentrations in roots, stems, and needles. In fine roots, however, soluble carbohydrate concentrations remained unaffected or increased by ozone fumigation. The only significant interaction was an antagonistic effect on root starch concentrations, where higher nitrogen levels alleviated the negative impact of ozone.     

臭氧对活性污泥特性影响研究

探讨了臭氧对于污水生物处理中活性污泥特性的影响。结果显示 ,随着臭氧化的进行 ,促进了活性污泥生物量的减少 ,并有一定量的生物污泥被无机化 ,并且污泥的活性和存活性降低了。其中臭氧投加量低于 0 .1gO3 /gSS时污泥活性即大幅下降 ,而后污泥浓度才随着臭氧量的增加而显著降低。     

臭氧预处理对剩余污泥特性及厌氧消化的影响

研究了臭氧预处理对剩余污泥特性及厌氧消化的影响,考察了臭氧投加量对污泥特性的影响,并进行了预处理后污泥厌氧消化产气的实验。结果表明,当臭氧处理时间为15 min时,污泥上清液中SCOD含量达到最高为1 006.08 mg·L-1,较未处理污泥提高了420.85%。污泥上清液中蛋白质和多糖含量在臭氧处理时间为10 min时达到最高。氨氮的含量在15 min时达到最大值。三维荧光结果显示随着臭氧投加量的增加污泥中的富里酸类物质有不同程度的减少,在臭氧处理时间为20 min时富里酸类物质减少量最为明显。显微镜和扫描电镜结果显示随着臭氧投加量的增加污泥中的微生物细胞结构受到了不同程度破坏。厌氧消化结果显示当臭氧处理时间为10 min时,污泥产甲烷率达到最高为318.39 mL·（g·VS）-1,较空白对照组提高了396.00%。